EdWaugh
Joined: 07 Dec 2004
Posts: 127
Location: Southampton, UK
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| Optimisation levels |
 Posted: Tue Jan 20, 2009 4:30 am |
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Hi all,
I've managed to get myself the latest version of the compiler and was having a play with the optimisation settings. I normally use 9 so I was trying 10 and 11.
At level 10 the following code gets broken and calculates incorrect results:
| Code: |
uint16_t generate_16bit_crc(uint8_t* data, uint16_t length, uint16_t pattern)
{
uint8_t* current_data;
uint16_t crc_Dbyte;
uint16_t byte_counter;
uint8_t bit_counter;
current_data = (uint8_t*)(data + 2);
crc_Dbyte = make16(data[0], data[1]);
for(byte_counter=0; byte_counter < (length-2); byte_counter++)
{
for(bit_counter=0; bit_counter < 8; bit_counter++)
{
if(!bit_test(crc_Dbyte,15))
{
crc_Dbyte <<= 1;
bit_test(*current_data, 7 - bit_counter) ?
bit_set(crc_Dbyte,0) : bit_clear(crc_Dbyte,0);
continue;
}
crc_Dbyte <<= 1;
bit_test(*current_data, 7 - bit_counter) ?
bit_set(crc_Dbyte,0) : bit_clear(crc_Dbyte,0);
crc_Dbyte ^= pattern;
}
current_data++;
}
for(bit_counter=0; bit_counter < 16; bit_counter++)
{
if(!bit_test(crc_Dbyte,15))
{
crc_Dbyte <<= 1;
continue;
}
crc_Dbyte <<= 1;
crc_Dbyte ^= pattern;
}
return crc_Dbyte;
}
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This is actually just the CCS CRC generator from v3. Setting opt to 9 makes this work correctly, at level 10 it calculates incorrect CRCs and at 11 I get the compiler error:
Internal Error - Contact CCS LABEL SCR=18907
I have also emailed CCS, any thoughts about this and what is the best opt level to stick to would be appreciated.
thanks
ed[/code] |
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